Classifications

• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F28—HEAT EXCHANGE IN GENERAL
  • F28F—DETAILS OF HEAT-EXCHANGE AND HEAT-TRANSFER APPARATUS, OF GENERAL APPLICATION
  • F28F19/00—Preventing the formation of deposits or corrosion, e.g. by using filters or scrapers
  • F28F19/004—Preventing the formation of deposits or corrosion, e.g. by using filters or scrapers by using protective electric currents, voltages, cathodes, anodes, electric short-circuits
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F28—HEAT EXCHANGE IN GENERAL
  • F28D—HEAT-EXCHANGE APPARATUS, NOT PROVIDED FOR IN ANOTHER SUBCLASS, IN WHICH THE HEAT-EXCHANGE MEDIA DO NOT COME INTO DIRECT CONTACT
  • F28D1/00—Heat-exchange apparatus having stationary conduit assemblies for one heat-exchange medium only, the media being in contact with different sides of the conduit wall, in which the other heat-exchange medium is a large body of fluid, e.g. domestic or motor car radiators
  • F28D1/02—Heat-exchange apparatus having stationary conduit assemblies for one heat-exchange medium only, the media being in contact with different sides of the conduit wall, in which the other heat-exchange medium is a large body of fluid, e.g. domestic or motor car radiators with heat-exchange conduits immersed in the body of fluid
  • F28D1/0206—Heat exchangers immersed in a large body of liquid
  • F28D1/022—Heat exchangers immersed in a large body of liquid for immersion in a natural body of water, e.g. marine radiators

Definitions

• the invention relates to a method and a system, respectively, for controlling biological growth on a bin cooler placed in a compartment according to the preamble of claims 1 and 11, respectively.
• the invention further relates to an assembly of a bin cooler and such a system, and to a vessel provided with such an assembly.
• the invention further relates to a method for installing such a system.
• Bin coolers are used more and more often in the maritime industry, where the advantages can be found in particular in the absence of a sea water circulation system.
• a bin cooler is a heat exchanger which is used on, for instance, sea-going ships, for cooling, for instance, the cooling water of ship's engines. Bin coolers are also used for heat exchange with coolant for other parts of an installation to be cooled. For the purpose of the cooling, heat exchange takes place between the coolant and the surrounding (sea) water.
• a bin cooler is arranged in a compartment (bin) of, for instance, a ship. In the inside of the compartment, a marine environment prevails. In the case of a ship, this is realized by means of openings in the ship's skin. The marine environment in the bin allows for external cooling of the coolant circulating in a closed system. Parts of the bin cooler are therefore exposed to different types of (sea) water.
• the biological growth is controlled by providing one or more copper anodes in the bin, in the proximity of the cooling elements of the bin cooler. These copper anodes are arranged in the bin in an electrically insulated manner relative to the grounding parts of the bin. The copper anodes are forcedly dissolved with the aid of a power source. Positive copper ions are then released which mix in the sea water and are carried along by the sea water flow along parts of the bin cooler. Owing to the dissolved copper ions, a toxic environment is created which hampers biological growth.
• the electric currents generated by the power source are discharged to, inter alia, surfaces of the bin and of the cooling elements, which then function as cathode surfaces.
• one or more steel cathode plates arranged at a small distance alongside the copper anodes are utilized. These steel cathode plates are welded or bolted to grounding parts of the closed space.
• a drawback of the known method and apparatus is that said manner of controlling biological growth entails an increased risk of formation of lime on various parts of the bin cooler and the bin. This can be explained as follows.
• lime layers of more than 2 cm are obtained. From literature, it further appears that at temperatures above 60 0 C, the calcium carbonates can form a significant layer, the more so when this happens in combination with a poor flow-through. It will be clear that such lime buildup can lead to a reduced efficiency of bin coolers, to machinery not functioning adequately and to unforeseen repairs and docking time.
• a method according to the preamble of claim 1 is characterized in that the method further comprises a decalcifying step alternating with the copper dissolving step, during which decalcifying step the metal containing element which is arranged in the compartment in an electrically insulated manner relative to grounding parts of the compartment, is set, via a second power connection, to an anodic potential, while the metal containing element decalcifies as a result of an occurring anodic reaction on the metal containing element and wherein the copper containing element functions as cathode.
• a system according to the preamble of claim 11 is characterized in that in operation, the metal containing element is arranged in the compartment in an electrically insulated manner relative to grounding parts of the compartment, and that the control unit is further designed for alternating between the copper dissolving operative condition and a decalcifying operative condition of the system, and for setting the metal containing element, via a second power connection of the system, to an anodic potential in the decalcifying operative condition, in which decalcifying operative condition the metal containing element decalcifies as a result of an occurring anodic reaction on the metal containing element, and the copper containing element functions as cathode.
• metal (M) of the metal containing element goes into solution according to the anodic reaction: M ⁇ M n+ + nev
• this formula would look as follows: 2Fe -> 2Fe 2+ + 4e-
• the metal (for instance iron Fe) of the metal containing element goes into solution on the surface and forms an oxide, it disengages itself and increases in volume to be carried along by the water flow together with the deposited lime layer.
• the metal containing element becomes, in a sense, sacrificial and can be replaced over time, for instance at the same time the copper containing element is replaced during, for instance, a regular docking service of a vessel. Owing to the alternation between the copper dissolving operative condition and the decalcifying operative condition, biological growth as well as buildup of lime layers is effectively controlled.
• the invention is further embodied in an assembly according to claim 13, in a vessel according to claim 14 and in a method according to claim 15 for installing a system.
• Fig. 1 schematically shows, in cross section, an example of an embodiment of a system according to the invention used with a bin cooler.
• Fig. 2 schematically shows an example of set current intensities used with an embodiment of a method according to the invention during copper dissolving and decalcifying method steps.
• a bin cooler 1 is shown which is arranged in a compartment 2, in this case a bin 2 of a vessel.
• the walls of the bin 2 are formed by the ship's skin 3 and partitions 4.
• the bin cooler 1 comprises cooling pipes 5 through which coolant flows.
• Arrows A and B indicate the locations where the coolant enters and leaves the bin cooler, respectively.
• Arrows C and D indicate the locations where, via the openings 6, the sea water enters and leaves the bin, respectively.
• heat exchange takes place between the coolant and the sea water.
• the bin cooler 1 is provided with a system for controlling biological growth on the bin cooler.
• This system comprises a control unit 7.
• two copper containing bars 8 are arranged. Each of these copper containing bars 8 is connected, with the aid of brackets 10, to carriers 21 connected to the walls 3, 4 of the bin 2.
• Insulating material 9 ensures that each bar 8 is arranged in an electrically insulated manner relative to grounding parts 21, 3 and 4 of the bin 2.
• the system further comprises a first power connection 11 which has an electric connection to a direct current source (not shown) and electric connections to the copper containing bars 8.
• the control unit 7 is designed for setting the copper containing bars 8, via the first power connection 11, to an anodic potential in a copper dissolving operative condition of the system.
• a copper dissolving operative condition positive copper ions 17 are released from the bars 8.
• the released positive copper ions mix into the sea water and are carried along with the sea water flow through the bin 2.
• a toxic environment is created in the bin 2.
• This toxic environment prevents biological growth in the bin 2 and on the bin cooler 2.
• three steel strips 18 are arranged. These strips 18 are supported by the carriers 21, while insulating material 19 ensures that each strip 18 is arranged in an electrically insulated manner relative to the grounding parts 21, 3, and 4 of the bin 2.
• the two bars 8 and the three strips 18 are arranged such that on both sides of each bar 8, a strip 18 is located. It is noted that instead of the three strips 18, also other numbers and shapes of metal containing elements can be utilized. Such elements can also be otherwise oriented, suspended and electrically insulated in the bin 2 relative to the grounding parts of the bin 2. During the above-mentioned copper dissolving operative condition of the system, the metal containing elements 18 arranged in the bin 2 function as cathode.
• the system further comprises a second power connection 12, which has an electric connection to a power source (not shown) and electric connections to the steel strips 18.
• the system further comprises a third power connection 14 which serves for realizing a grounding connection with grounding parts 3, 4, 21 of the bin 2.
• the control unit 7 is designed for alternating between the copper dissolving operative condition and a decalcifying operative condition of the system, and for setting the steel strips 18, via the second power connection 12, to an anodic potential in the decalcifying operative condition.
• the control unit 7 is designed for mutually alternating said copper dissolving operative condition with a decalcifying operative condition of the system and for setting the steep strips 18, via the second power connection 12, to an anodic potential in the decalcifying operative condition.
• the alternation between the operative conditions may be realized by, for instance, having the control unit 7 reverse the polarity of electric connections connected to a direct current source of the first power connection 11 and the second power connection 12.
• the steel strips 18 decalcify as a result of an anodic reaction occurring on the steel strips 18, i.e. the anodic reaction 2Fe ⁇ 2Fe 2+ + 4e- More in general, instead of one or more steel strips 18, one or ore metal containing elements can be used.
• metal (M) of the metal containing elements goes into solution according to the anodic reaction: M ⁇ M n+ + ne ⁇
• the metal (for instance iron Fe) of the metal containing element goes into solution on the surface and forms an oxide, it disengages itself and increases in volume to be carried along by the water flow, together with the deposited lime layer.
• the copper containing bars 8 each function as cathode.
• the following cathodic reaction occurs: O2 + 2H2O + 4 e ⁇ 4OH ⁇
• the insulating material 19 prevents an uncontrolled electric connection between the steel strips 18 and the grounding parts 21, 3 and 4 of the bin 2.
• Fig. 2 Figure shows an example of current intensities I, utilized with an embodiment of a method according to the invention, set by the control unit 7, represented in Ampere, as a function of the time T, represented in minutes.
• a positive current intensity I the current intensity is indicated of the electric direct current through the copper containing bars 8 set to an anodic potential during the copper dissolving operation of the system.
• a negative current intensity I the current intensity is indicated of the electric direct current through the steels strips 18 set to an anodic potential during decalcifying operation of the system.
• the current intensity I during each of successive, continuous time intervals is, each time, set to a constant value, while at a transition from such a time interval to a following similar time interval, the set constant value, each time, staggers step-wise.
• Il is also called high current intensity, 12 low current intensity and 13 extra high current intensity.
• the duration of the time intervals in which the values II, 12 and 14 are set is, each time, 15 minutes, and the duration of the time intervals in which the value 13 is set is, each time, 30 minutes.
• the high and low current intensities Il and 12 are set and then the extra high current intensity 13 is set.
• the high current intensity Il is understood to be sufficiently high to generate sufficient ionic copper to resist marine growth, for instance to prevent a barnacle from attaching itself.
• the high current intensity Il is alternated with the low current intensity 12.
• the duration of the time intervals in which the low current intensity is set (in the example, 15 minutes), is adjusted to the minimum time required for, for instance, a barnacle to attach itself.
• the use of the low current intensity 12 further offers the advantage that the amount of dissolved copper is reduced so that the copper containing bars 8 need to be replaced less rapidly.
• the copper containing bars 8 are set to an anodic potential thus that during the copper dissolving step, periods with high current intensities Il occurring through the copper containing bars 8 alternate with periods with low current intensities 12 occurring through the copper containing bars 8.
• Suitable values for the latter high current intensities Il can be determined depending on the total cooling surface of the bin cooler. For instance, in some circumstances, a high current intensity Il of approximately 3.0 Ampere can be suitable for a total cooling surface of the bin cooler of approximately 100 square meters, while, in comparable circumstances, a high current intensity Il of approximately 0.3 Ampere can be suitable for a total cooling surface of the bin cooler of approximately 10 square meters. It has appeared that the latter low current intensities 12 are preferably between 20% and 40% of the high current intensities.
• the copper dissolving operative period is terminated with a set extra high current intensity 13 for a time interval of 30 minutes (boost period).
• boost period a set extra high current intensity 13 for a time interval of 30 minutes
• the decalcifying operative period commences, in which, for 15 minutes, the negative current intensity 14 is set.
• the copper containing bars 8 are set to an anodic potential such that the copper dissolving step comprises a boost period with extra high current intensities 13 relative to the high current intensities mentioned occurring through the copper containing bars 8. It has appeared here that the latter extra high current intensities 13 are preferably between 130% and 200% of the high current intensities II. It is then further advantageous that the decalcifying step links up with one of the periods with high current intensities occurring through the copper containing bars 8 or with the boost period, the latter boost period being preferred.
• negative current intensities 14 utilized during the decalcifying step are preferably between minus 130% and minus 200% of the high current intensities II.
• the copper dissolving operative period recommences, preferably with a set high current intensity II, as in the example, or with a set extra high current intensity 13.
• An advantage of applying the high or the extra high current intensity directly after the completion of the decalcifying operative period is that thus, control of the marine growth is intensified as a counterbalance to the preceding decalcifying operative period in which no copper was dissolved and the marine growth might have developed too rapidly.
• the duration of the time intervals in which the current intensity 14 is set is tuned to the minimum period required for, for instance, a barnacle to attach itself.
• control unit of a system according to the invention such as the control unit 7 of the system described with reference to Fig. 1, may be designed for carrying out methods according to the invention which were described in the foregoing on the basis of Fig. 2.
• the system for controlling biological growth described thus far can also be designed for operatively controlling the potential difference between the (sea) water and the bin cooler, and/or grounding parts, to set values, for the purpose of the cathodic protection mentioned.
• the latter control also prevents the potential difference from becoming too great, in which case an increased risk of lime formation on the bin cooler or the bin would arise.
• the system shown in Fig. 1 is provided with a reference cell 20 which operatively measures the potential difference, and the control unit 7 is designed for preventing a set maximum allowable potential difference between the (sea) water and the bin cooler or the grounding parts from being exceeded.
• the reference cell 20 is arranged on a partition 4 of the bin 2.
• the reference cell 20 is connected via a communicative connection 15 to the control unit 7.
• the system comprises a controlled connection which, each time the potential difference measured by the reference cell 20 threatens to exceed the set maximum or fall below a set minimum, temporarily leads current to the grounding parts 21, 3, 4 of the bin 2, or interrupts this, so that the potential difference between the (sea) water and the bin cooler or the grounding parts is optimized and the set maximum potential difference is not exceeded.
• This temporary current is taken off the power circuit which electrically interconnects the steel strips 18 and the copper containing plates 8, in the example shown via the first and second power connection 11 and 12.
• the controlled connection can comprise, for instance, a switch 22, accommodated in the control unit 7, which, depending on the potential difference measured by the reference cell 20, either brings about or removes a connection between the second power connection 12 and the third (grounding) power connection 14.
• the reference cell 20 can further comprise a temperature sensor, so that measured temperatures can be transmitted to the control unit 7. Temperature sensors communicatively connected to the control unit 7 can also be provided at other locations in the bin 2, for instance integrated in the copper containing bars 8. The temperature measured by such temperature sensors can be saved for, for instance, registration in an electronic memory so that, afterwards, it can be verified which temperatures have prevailed at locations in the bin 2. The measured temperatures can also be used by the control unit for controlling, depending on the temperatures, the set current intensities and/or the above-mentioned set value of the potential difference between the (sea) water and the bin cooler, or the walls of the bin. In this manner, the temperature dependency of the chance of lime formation can be taken into account. It is, for instance, known that the risk of lime formation increases significantly at temperatures above 60 0 C, while it is also known that the risk of marine growth at this kind of temperature decreases significantly.
• control unit can comprise various control components, of which individual control components or groups of control components in a joint housing, or in several housings, may or may not be directly or indirectly communicatively interconnected.
• control components of which individual control components or groups of control components in a joint housing, or in several housings, may or may not be directly or indirectly communicatively interconnected.
• many variations are possible in, for instance, the number of the differently set current intensities, in the values of the differently set current intensities and in the duration of the different time intervals in which the different current intensities are used.
• boost periods more often or less often during the copper dissolving operative conditions.

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• Engineering & Computer Science (AREA)
• Physics & Mathematics (AREA)
• Thermal Sciences (AREA)
• Mechanical Engineering (AREA)
• General Engineering & Computer Science (AREA)
• Ocean & Marine Engineering (AREA)
• Electrolytic Production Of Non-Metals, Compounds, Apparatuses Therefor (AREA)
• Prevention Of Electric Corrosion (AREA)
• Agricultural Chemicals And Associated Chemicals (AREA)

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• 2006
  • 2006-09-18 NL NL1032531A patent/NL1032531C2/nl not_active IP Right Cessation
• 2007
  • 2007-09-18 EP EP07808587A patent/EP2069704A2/en not_active Withdrawn
  • 2007-09-18 WO PCT/NL2007/050456 patent/WO2008035969A2/en active Application Filing

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